ABSTRACT
Weizhou Island, located in the northwestern South China Sea (SCS), is the largest volcanic island in China. Its eruption represents the most recent volcanic activity in and around the SCS. We determined whole-rock major- and trace-element contents and Hf–Sr–Nd–Pb isotope compositions of Quaternary basalts fromWeizhou Island to provide insights into the nature of theirmantle sources and formation processes. These basalts have SiO2 contents of 48.21 to 50.04 wt% and belong to the alkaline series. The basalts bear the signature of typical oceanisland basalt, being characterized by enrichments in large-ion lithophile and high-field-strength elements, clear differentiation of light rare-earth elements (REEs) from heavy REEs ((La/Yb)N = 15.19–19.29, mean of 16.82), and show no obvious Eu anomalies (Eu/Eu* = 0.98–1.17, mean of 1.04). Hf–Sr–Nd–Pb isotope compositions show that the mantle source of these basalts can be regarded as a mixture of a depleted MORB mantle source and enrichedmantle 2 (EM2), with geochemical data supporting an origin of theEM2 end-member fromthe Hainan mantle plume. Combining the new results with previous findings, we propose that Cenozoic intraplate volcanism in the SCS and surrounding areas is related to the magmatic activity of a large igneous province and thatthis province is associated with the Hainan mantle plume.
